Supervision of radio signaling systems



J. R. MacKAY 2,165,064

SUPERVISION OF RADIO SIGNALNG SYSTEMS Filed June 20, 1956 5 Sheets-Shes*l 1 July 4, 1939.

M ATTORNEYS.

NVP d- INVENTOR.

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.1. R. MacKAY 2,165,064

SUPERVISION OF RADIO SIGNALINC'SYSTEMS Filed June 20, 1936 3 Sheets-Sheet 2 Rw S Y mw M mlm@ Ew R H V m 2 .T m RWA /7 www@ foei n Y Am T. P M B A M/|| mi A. P m/f/fM c AA Uil 1l .a RL z /Wm 5o A au ,51-1 cmw 2 o 2 7 l O 2 w o M 3 DN DN m m m m /m 1 T m w m E .IL om woz W 5 1.a

July 4, 1939.

July 4, 1939. J. R. MacKAY 2,165,064

SUPERVISION OF RADIO SIGNLING SYSTEMS Filed June 20, 1956 3 Sheets-Sheet 3 TRANSMITTER,

Boe osclLLA-rmz REMOTE- TRANSMITrER .lll

506 OSCILLATOE TRANSMWTER INVENTOR. 0 MM fa WMM/w1 BYcvvPIA, Kw MLM da ATTORNEYS.

Patented July 4A,

UNITED STATES PATENT OFFICE SUPERVISION OF RADIO SIGNALIN G SYSTEM Application June 20, 1936, Serial No. 86,270

29 Claims.

This invention relates to the supervision of radio signaling systems, and in more specic aspects to receiving stations thereof having provision for automatic response to calling or other signals, and wherein the receiving apparatus is monitored, or otherwise supervised at desired times.

One of the objects of the invention is to provide a radio signaling system in which the receiving apparatus is arranged to listen in continually or intermittently in order to control an alarm bell or other apparatus, automatically, in response to a predetermined signal transmitted by radio waves from a remote transmitter, such as, for example, a distress signal, and wherein means are provided for automatically and intermittently monitoring or checking the entire receiving system, including its capability of automatic response to and control by the predetermined remotely transmitted signal. A further object of the invention is to provide new means and combinations of instrumentalities for supervising the responsive conditionof a radio receiver and its associated equipment (and to operate an alarm or other apparatus upon failure thereof), thereby checking the functioning of many or all of the several instrumentalities and power sources of the receiving apparatus, such as the tuning of the ref ceiver to a desired carrier frequency, both the activation and the lament life of the vacuum tubes, and the condition of transformers, condensers, resistors, connecting circuits, and batteries.

Further objects are: to provide a radio receiving station in which the presence of atmospheric or other disturbances sufficient to prevent reception of desired radio signals will be automatically determined, and will cause operation, for example, of a suitable warning signal; to provide means and combinations of instrumentalities which, for eecting supervision or monitoring, in the foregoing and other respects, can be readily applied to any of the usual or standard types of receiving apparatus, particularly automatic radio calling systems or like systems wherein an alarm or other apparatus is to be automatically controlled by radio waves transmitted from a remote point; and to provide new combinations of instrumentalities and new sub-combinations thereof, for the purposes above stated, which are in themselves relatively simple in operation, and thoroughly reliable, and which obviate or reduce the necessity of frequent personal inspection of a radio receiving station by an attendant or operator.

Other objects and advantages will appear as (Cl. Z50-20) some of the preferred forms of the invention are hereinafter described.

Referring to the drawings which illustrate what I now consider to be preferred forms of the invention:

Figure 1 is a wiring diagram of the receiving station of an automatic radio calling system;

Figure 2 is a projected plane section of certain switch operating cams, to show their timing;

Figure 3 is a wiring diagram of another form of radio signaling system; and

Figures 4, 5 and 6 are respectively Wiring diagrams of somewhat further modified forms of radio signaling systems.

Referring rst to Figure l, the receiving station here shown is of the type in which the radio wave receiving apparatus proper, generally designated A, is adapted to be tuned and set for reception of a desired radio signal, so that in response to that signal the receiver will automatically bring into operation apparatus such as the alarm bell B. In the specic apparatus shown, it is contemplated that upon reception of a carrier having a predetermined radio frequency and modulated at a predetermined audio frequency, the alarm bell will ring to indicate that a call is being received. The radio receiving apparatus itself may be of any suitable type, embodying, for example, the usual vacuum tubes and the usual tuning and other circuits for selecting, amplifying at radio frequency, detecting, and amplifying at audio frequency, the signals picked up by the antenna system C. As shown here, the receiving apparatus is further understood to include suitable power supply elements, of which many types are known in the art, for deriving the necessary filament, plate, and other power from a standard 11G-volt line. It is also preferable but not essential that the receiving apparatus include an automatic volume control device or be of a circuit arrangement, such as the super-regenerative type, having automatic volume control inherent in its design. i

The alarm bell is operable under control of a suitable resonance relay, generally designated D, which is in turn brought into operation under the control of a relay amplier E coupled to the output of the receiving apparatus. Preferably the relay amplifier is designed to respond to an audio frequency E. M. F. set up by the receiver, and to deliver to the relay a pulsating direct current, or a succession of direct current impulses, having a frequency corresponding to that impressed upon the relay amplier, and thus to the audio frequency at which incoming radio frequency oscillations are modulated. The resonance relay, in turn, is tuned for response only to that specic audio frequency, viz., that of the particular call modulation to which the station is intended to respond.

There is further provided a local source of modulated radio frequency oscillations generally designated F, which is preferably inherently stabilized as to frequency and which may include a vacuum tube oscillator, and may have a modulating device such as the microphone hummer it). The radio frequency oscillator here shown is of the crystal controlled type, although other inherently stable oscillators, for example the Dynatron, can be satisfactorily employed. In general, this oscillator may be similar in physical size and characteristics to the oscillators used for frequency conversion in superheterodyne receivers. The microphone hummer iB may likewise be replaced by any other modulating device, such as a. simple constant frequency generator or buzzer, or a vacuum tube audio oscillator. In fact, in some cases, it is possible to dispense with a separate modulator, and to make the vacuum tube oscillator self-modulating by the inclusion of a secondary circuit tuned to a lower or audio frequency, as is known in the art. The oscillator also includes an adjustable attenuating device l i, through which the modulated oscillations are impressed upon the input of the receiving apparatus.

There is further provided a cycling mechanism, generally designated G, and operated by a continuously driven motor l2, for intermittently bringing into play the supervision of the receiving apparatus and also, if desired, for intermittently placing the receiving apparatus in operative condition-i. e., so that the receiver intermittently and automatically listens in for calls from the remote transmitter, and so that there is effected a saving of energy consumption and of wear and tear on the various receiver elements, in the manner described in my copending applications Serial Nos. 730,127 and 11,783, entitled Communicating systems and respectively rlled on June l1, 1934 and March 19, 1935.

Assuming that the cycling mechanism controls both the Vreceiving apparatus and the supervising instrumentalities, it is arranged, as is hereinafter particularly explained, so that at periodic intervals it eects energization of the receiver A, the oscillator F, and the other associated elements, brings about a further modulation of the oscillations set up by the oscillator F (to make them simulate the call signal of the remote transmitter), and so disposes the alarm bell under control of the resonance relay D that if the oscillator F has impressed upon the input of receiving apparatus the local signal properly simulating both the radio and audio frequency characteristics of the call signal of the remote transmitter, and if the receiving apparatus is in proper working condition to respond to such a call, the resonance relay will be energized and operate to prevent actuation of the alarm bell, otherwise biased to go into operation. Following this supervising period, wherein any failure of the receiving apparatus, or its vacuum tubes, power supply, tuning or other circuits, will ring the alarm bell and advise the attendant that something is wrong, the cycling mechanism then cuts oi operation of the oscillator F, and during a listening period, so connects the alarm bell as to cause the latter to ring if a call is then received from a remote transmitter.

As will now be appreciated, the cycling mechanism can be arranged to provide these testing and listening-in periods at intervals oi any desired duration; here, for instance, it is assumed that a lO-second testing period and a 30-second listening-in period are desired every 15 minutes. Switching means are also provided for operating the receiving apparatus without any supervision at all, and also for placing the receiving apparatus continuously in listening condition, subject only to the provision of intermittent testing periods by the cycling mechanism--an arrangement peculiarly desirable where the apparatus is used to provide an automatic SOS reception alarm on shipboard.

The attenuator I l is adjusted to permit introduction of the signal locally generated by oscillator F into the receiving apparatus at such a level of intensity as will cause the receiving apparatus and its associated ampliiier E and relay D to respond in spite of a predetermined permissible maximum atmospheric or noise level. In this way, the arrangement is such that if static or other outside disturbance is so intense as would prevent normal reception of a calling signal, it will have the same effect on the locally generated signal and thus, during the testing period, cause operation of the alarm bell. The attendant will then be summoned and will learn, upon manual operation of the receiving apparatus, that atmospherics or the like are so heavy as to prevent normal automatic call repection.

Referring more particularly to the specific apparatus shown in Figure i, it will be appreciated that the radio receiver is coupled to the antenna through a suitable conductor i3, and is equipped with a loudspeaker lil, or like communication translating device, such as a telephone receiver. It may also be preliminarily explained that whereas the selective relay D, coupled by conductors i5 and IS to the output of the relay amplifier E, is here designed for response to a modulating frequency of, say, iive cycles per second imparted by the cam il which is driven by the motor l2, any other suitable selective signal response device may be similarly coupled to the conductors l5 and i6, and the cam Il so designed as to interrupt or modulate the local testing oscillations set up by oscillator F, in simulation of the signal to which the selective signal response device is intended to respond. For example, the relay D may be replaced by a device which will close an alarm-controlling circuit upon reception of a prescribed type of SOS signal, and cam il would then be arranged, with its associated instrumentalities, to operate as an automatic key for local transmission of that prescribed signal by the oscillator F.

The motor l2, for operating the cam I1 and the cycling mechanism, may be of any suitable type which is reasonably constant in speed, I prefer at present to employ a motor of the magnetic type, such as that described and claimed in United States Patent No. 1,985,357, for Electric motor apparatus, granted December 25, 1934, upon the application of Charles F. Wallace. As a motor of that type can be made to run on approximately 75 watt-hours per year, motor l2 is operated continuously, its energizing circuit being as follows: from the positive side of a suitable power source, such for example as a 6-volt battery as indicated, through the conductor I8,

motor I2, and through the conductor I9, back to the negative side of the 6-volt battery.

There are conveniently provided two multiple pole switches 20 and 2| for bringing the receiving apparatus and the various testing instrumentalities selectively into operation in various ways. Switch 20, for example, is of the four-pole, three-position type, and in its right-hand position arranges the receiver A and the loudspeaker 4 for preliminary testing operation which will include a test of the speaker and will enable the operator to adjust the receiver tuning. In its central position, switch 20 connects the receiving apparatus through the relay amplifier E to the selective relay D, for automatic call operation, and with the switch 20 in its left-hand position, the receiver is connected directly to the loudspeaker |4, or like device, for direct' manual operation-i, e. under the immediate personal attendance of an operator who personally listens for calls, as is the case on shipboard, for example, when the operator is on watch-and the automatic call-response and monitoring features of the system are not brought into play. Switch 2|, for controlling the cycling and supervising devices, is adapted, when in its right-hand position, to condition these devices for preliminary tests of the receiving apparatus and other instrumentalities. In its central position, switch 2| connects the receiver for continuous operation, while bringing into play the intermittent monitoring thereof, and when turned to its left-hand position, switch 2| brings the station into full automatic intermittent operation-i. e., so that the cycling mechanism G both tests the receiver and causes it to listen in for calls, only at' predetermined periodic intervals.

The construction and connections may now be further explained by describing a characteristic set of operations of the system shown in Figure 1.

Let it be first assumed that the operator or attendant, as on shipboard, is going off watch and desires to leave the apparatus in condition for automatic response tc an incoming call. As it is first desired to determine whether the receiver and monitoring system are functioning properly throughout, he rotates the selector switches 20 and 2| to their extreme right-hand or test positions. By this operation the receiving apparatus A and various other instrumentalities are energized, as will now be explained.

The following circuit is established to connect the receiving apparatus with the 11G-volt line: from the negative side of the 11G-volt line through conductor 22 to one side of the receiver power input, and from the other side of the receiver power input through conductor 23, switch arm 24 of switch 2|] (now in its right-hand position), switch point 25, conductor 26, switch arm 21 of switch 2| (now in its right-hand position), switch point 28, and through conductor 29 back to the positive side of the 11G-volt line. With the 11G-volt line thus connected to the power input of the receiver, the power supply elements of the latter, as previously explained, bring it into full operative condition.

The following circuit is also established upon rotation of switch 2| to its right-hand position: from the negative side of the 6-volt battery, through the conductor 30, respectively through the condutors 3| and 32, to one side of each of the vacuum tubes 33 and 34, and from the other side of the laments of said tubes, through conductors 35 and 35a respectively (the laments of these tubes being connected in parallel, as will be understood), through conductor 36, switch point 31 and switch arm 38 (of switch 2|) and through conductor 39 back to the positive side of the 6- volt battery. By the circuit just traced, the filaments of the oscillator tube 33 and the relay amplifier tube 34 are energized, and the relay amplifier E is brought into operative condition, since plate current therefor is supplied in the following circuit: From the positive side of a suitable source of plate current, such as the B battery indicated, through conductors 40 and 4|, through the primary winding 42 of the audio frequency output transformer 43, to the plate of tube 34, and from the cathode of the tube 34 through the biasing resistor 45 to ground, and thereby back to the negative side of the B battery, connected to ground through the conductor 4G.

The following circuit is also established at this time: from one side of the output of t'he receiving apparatus, through conductors 41 and 48, loudspeaker I4, conductors 49 and 50, switch point 5|, switch arm 52 of selector switch 20 (now in its right-hand position), and through conductor 53, back to the other side of the receiver output. At the same time a circuit is like- Wise established from one side of the receiver output through conductors 41 and 54, through the primary winding of the input audio frequency transformer 56 of the relay amplifier E, conductor 51, switch point 58, switch arm 59 of switch 2|) (now in its right-hand position) and through conductor 53 back to the other side of the receiver output. In this manner, with switch 20 in its right-hand position, both the loudspeaker 4 and the input of the relay amplifier E are connected in parallel to the output of the receiving apparatus A.

It may here be explained that means are provided for supervising the circuit of the motor mechanism |2, so as to afford operation of an alarm upon any failure of this mechanism to maintain its required operation. To this end, a centrifugal switch 60 is mounted on the shaft of the motor |2, and although this switch may be of any suitable type, I prefer to employ one which consists of an eccentric bushing, normally rendered concentric with the motor shaft by means of the governor weights 6| and E2 when the motor is driving the shaft at the proper speed of rotation. Under such circumstances, i. e., when the bushing is concentric with the shaft, contacts 63 and 64 are maintained open, but when the motor slows down or stops these contacts will intermittently or permanently close and thereby energize relay 65 in the following circuit: from the positive side of the 6-volt battery through conductors I8 and 65, through the relay 65, conductor B1, contacts 64 and 63 (now closed) and through conductors 68 and I9, back to the negative side of the 6-volt battery. Energize.- tion of relay 65 will cause its contacts 69 and 10 to close, establishing the following circuit: from the positive side of the G-volt battery, through conductor |8, contacts 69 and 15 (now closed) of relay 65, through conductors 1| and 12, alarm bell B, and through conductors 13 and 30, back to the negative side of the 6-volt battery. Thus if the motor mechanism stops or fails to drive its shaft at the predetermined speed, such failure will be announced by the alarm bell B, brought into operation by the instrumentalities just described.

Referring again to the setting of the selector switches for preliminary testing: rotation of switch 2| to its right-hand position also causes energization of the modulator relay T4 in the following circuit: from the positive side of the 6- volt battery, through conductors 39 and 15, switch arm i6, .and switch point Ti (of switch 2i), conductor 18, relay l, and through conductor 3D back to the negative side of the 6- volt battery. The armature of relay i4, attracted upon energization of the latter, is afliXed to a switch plate 79, which is pivoted on the pin and is moved counterclockwise with the .armature, so that the switch operating spring or arm 8! is brought into engagement with the surface of cam li, and continuing rotation of the latter thereafter causes the switch arm 8l to close contacts 82 and d3 each time the switch arm rides over .a high spot on the cam. With this arrangement, the switch arm 8l is only brought into engagement with the rapidly rotating cam il at times when it is desired to effect modulation of the oscillator F; although in some cases this arrangement may be dispensed with, it provides an effective means for reducing wear and tear on these parts.

Assuming that the periphery of cam Il is so designed that its teeth are caused to operate the cam switch 8l five times per second, it will be seen that the cam and cam switch, together with the circuit controlled thereby, provide means for setting up .a modulating frequency of 5 cycles per second. Each time the contacts 82 and 83 of the cam switch are closed, there is brought into play a modulating device such as the microphone hummer IB, in the following circuit: from the positive side of the 6-volt battery, through conductors 3Q and l5, through switch arm l of selector switch 2l, switch point l?, conductors i8 and Sii, contacts S2 and 83, conductor B5, the microphone hummer l (including its primary), and through conductors 86 .and 3&3, back to the negative side of the 6-volt battery. It will be seen that an alternating current of characteristics dictated by the cam ll (e. g., in this instance 5 cycles per second) will now be induced in the secondary ita of the microphone hummer, and since the latter is connected with the grid of the oscillator tube 33, .as in the manner shown, corresponding modulation will be eected upon the radio frequency oscillations produced by tube 33 when and if plate current is applied to the oscillator tank circuit.

It will be understood that all of the operations just described as taking place upon the positioning of switches 28 and 2i in their right-hand positions will occur .at once. After waiting a reasonable time for the filaments or cathodes in the receiver, oscillator and amplifier tubes to heat up, the operator noW tests his equipment for response to a calling signal by depressing in succession the test switches 8l and 88.

If the receiver is properly tuned to the desired calling signal, and the monitoring equipment is in proper condition, depressing test switch 8l' will cause operation of the .alarm bell B, in the manner now to be described.

When switch 8l is depressed, plate circuit supply is established to the oscillator F, through the following circuit: from the positive side of the B battery, through conductors il@ and 8S, contacts Sil and 9! of switch 3l (now closed), conductors S2 and 93, contacts $34 and S5 (noW closed) of test switch 8S, through conductor 96, to the plate circuit of the oscillator tube 33, and thence through the tube to ground, and through conductor 4S back to the negative side of the B battery. Thus energized, the oscillator F, frequency-stabilized by the piezo-electric crystal 96a, generates a radio frequency carrier modulated by the microphone hummer i6 in accordance with the audio frequency note of the latter and in accordance with the signal characteristics (here, 5 cycles per second) imparted by the cam ll. Through the attenuator I l, which preferably comprises a coupling condenser and an adjustable non-inductive resistor connected as shown, the modulated radio frequency output of the oscillator is carried by conductor and impressed upon the radio receiving apparatus A, through a coupling device Qld, connected, for example, to the antenna lead I3. The coupling device @la may be any suitable type, such as an inductive coupling, or such .as the condenser arrangement shown, having one plate connected to the conductor i3 and the other to conductor 9?- such a condenser being preferably variable. some cases, a loose coupling device or a preselector (which may include a radio frequency amplifier stage) or the like may be interposed between the .antenna and the point where they oscillator is coupled to the receiver; such an I arrangement serving to block oil such radiation of locally generated test signals as might otherwise occur from the antenna and might, for example under extreme circumstances, cause a false operation of another and nearby call-receiving station.

The conductor Sl is preferably shielded, as indicated at the attenuator ll, with which the shielding d8 cooperates, is preferably so adjusted that the intensity of the modulated oscillations received by the receiving apparatus A from the oscillator F is reduced to a value equal to the lowest signal intensity which will satisfactorily operate the receiving apparatus and the parts controlled therefrom, under a predetermined maximum severity of atmospheric conditions.

In other words, the local signal thus impressed upon the receiver (from the oscillator F) is no stronger than is necessary to operate the receiver' until such time as static or other disturbances become so severe that automatic listening-in equipment would not function properly; when static or the like reaches such an intensity as would prevent response to a signal from a distant station, it

will also prevent response to the local signal,

with the consequences which are hereinafter eX- plained as resulting from a failure of response to the local signal in accordance with the manner in which it is used for testing.

It will now be seen that when test switch 8l is depressed, a modulated local signal is generated by the oscillator F, received and amplified by the receiving apparatus A, and impressed upon the loudspeaker lli and also upon the input of the relay amplier E. In response to the modulated signal, the relay amplifier thereupon delivers an alternating current (alternating at the frequency of microphone hummer Eil and broken or modulated at the frequency imparted by cam il) to the input of the rectier 99, which is connected to the secondary lii of the rela-y output transformer 33, through conductors liii and M2. Preferably the rectifier 99 is of the full wave type, comprising four groups of copper oxide rectifier elements in the usual bridge connection, although other suitable rectiers may be used, or a vacuum tube, with its grid normally biased to cut-off, can be employed.

By the rectifier 99 the alternating current 5- cycle pulsations are converted to vdirect current Inv impulses which have a corresponding frequency or rate of five per second and which are delivered to the winding |03 of the selective relay D, through conductors I5 and I5. This selective relay is preferably of the torsional pendulum type mechanically tuned to respond to a predetermined modulation frequency which is the same as the modulation frequency produced by the cam I1 and the modulation frequency of the calling carrier which is to be received from a remote station. Other types of relays may be employed, although it is of advantage, in an automatic call receiver, to have the local signal simulate the predetermined call signal, and to have the relay thus responsive to both local and remotely transmitted signals, so as to aiford supervision of the relay as well as the receiver. Preferred forms of the relay here shown are described in my aforesaid copending application, Serial No. 730,127, and in the pending application of Charles F. Wallace, Serial No. 82,724, for Selective relay.

Inasmuch as the periodicity or rate of the impulses traversing the Winding |03 of the relay D corresponds to the frequency to which the relay is tuned, the latter is periodically energized and periodically closes its contacts |04 and |05, to energize relay |06 in the following circuit: from the positive side of the 6-volt battery, through conductors 39 and |01, contacts |04, |05, through the limiting resistance |08, conductor |09, relay |06, and through conductors I0, 13 and 30, back to the negative side of the G-volt battery. A condenser III is preferably connected across the winding of relay |06, so that its armature is continuously attracted during the periodic openings and closures of the contacts |04 and |05, even though the current impulses supplied by such periodic closures are of relatively short duration. It will also be understood that the limiting resistor |08 limits the inrush of current to the condenser III, and thereby prevents damage to the contacts |04 and |05, as by excessive arcing` Energization of the relay |06 causes its contacts ||2 and ||3 to close and operate the alarm l 'j bell B in the following circuit: from the positive side of the 6-volt battery, through the conductor 39, the switch point 31 and arm 38 (now closed) of the selector switch 2 I, through the conductors 36 and I I4, through the normally closed contacts I5 and I I6 of the alarm switch I I1, through the conductor I I8 and now closed contacts I I2 and I I3 of the relay |06, through the conductor I|0 and the normally closed contacts |20 and |2| of the cam switch |22, through the conductors |23 and 12 to f3 one side of the alarm bell B, and thence via the conductors 13 and 30 back to the negative side of the 6-volt battery.

As the winding of the relay |24 is in parallel with the alarm bell B, relay |24 is also energized upon establishment of the foregoing circuit, being established, and by the closure of its contacts |25 and |26, continues its own energization and the energization of the alarm bell until the alarm reset switch I1 is depressed, and even though the 1 selective relay D subsequently becomes de-energized. The circuit so established is as follows: from the positive side of the S-volt battery, through conductor 39, switch arm 38 of selector switch 2|, switch point 31, conductors 36 and II4, normally closed contacts ||5 and IIB of the alarm reset switch ||1, conductor IIB, contacts |25 and |26 (now closed) of relay |24, thence through the alarm bell B and relay |24 in parallel, and through conductors 13 and 30 back to the negative side of the -volt battery.

The alarm bell thus continues to ring, indicating that the receiving apparatus is in full cperative condition and is properly tuned to the radio frequency of the local signal (and thus to the equivalent radio frequency of the anticipated remotely transmitted signal), and that the relay amplifier and selective relay are properly responsive to the modulating characteristics of the local signal (and thus, again, to the equivalent modulating characteristics of the remotely transmitted signal). It will also be understood that during the time that key 81 is depressed, a further check on the receiver is afforded by the conversion of the local signal to sound in the loudspeaker I4; in fact, the operator can then accurately set the receiver on frequency by listening to the local signal through the loudspeaker and tuning the receiver for maximum loudspeaker volume.

The operator now depresses the alarm reset switch III, which opens the energizing circuit for alarm bell B and relay |24, thus turning off the bell.

The operator next depresses the test key 88 in order to check for receiver failure response, i. e., to check the circuit which would energize the alarm upon receiver failure in a later test. Contacts 94 and 95 are thereby opened, interrupting the supply of plate current to the oscillator even if certain normally open contacts of the cycling mechanism (hereinafter described) that moment happen to be closed. Oscillator F then fails to transmit the local signal, and response of selective relay D is thus prevented, so that contacts I|2 and |28 of relay |06 remain closed. v

Depressing key 88 also closes its normally open contacts |29 and I 30, establishing the following circuit through the alarm bell B: from the positive side of the 6-vo1t battery, through conductor 39, switch arm 38 of selector switch 2|, switch point 31, conductors 36 and |I4, normally closed contacts I5 and I I6 of the reset switch II1, conductor ||8, contacts ||2 and |28 (now closed) of the now de-energized relay |06, conductors |3I and |32, contacts |29 and |30 (now closed) of the test key 88, conductors |21 and 12, alarm bell B, and through conductors 13 and 30, back to the negative side of the 6-volt battery. The alarm bell B is thus caused to ring, indicating proper functioning of the circuit through contacts I|2 and |28 (of relay |06) which, in subsequent supervision or monitoring, would be employed to energize the bell upon failure of the receiving apparatus; operation of the bell at this time also indicates, among other things, that contacts |04 and |05 of relay D are properly open when no signal is delivered to the relay by the receiver.

Thereupon, key 88 is permitted, as was key 81 after the previous test, to be restored, by its inherent resilience, to normal, non-testing position, and alarm reset switch I I.' is again depressed to open the alarm lock-in circuit established by relay |24, and thus to turn off the bell.

Assuming that the above test have demonstrated that the receiver and monitoring apparatus are functioning properly, the operator may then turn the selector switch 20 to its central or automatic position, and the selector switch 2| to its extreme left-hand or intermittent position, so that thereafter and automatically, the receiver is intermittently monitored for response to the local signal, and intermittently conditioned to listen-in for calling signals from the remote transmitter. To provide this intermittent operation, a cam switch |33 is actuated by cam should at 1 |34, and the cam switch |22 is similarly actuated by cam |35, cams |34 and |35 being driven in synchronism by the motor mechanism I2, and at a rate corresponding to that at which it is desired to repeat the testing and listening-in periods. It is here assumed, for example, that each cam makes one revolution in 15 minutes, so that a testing period and a listening period are provided every 15 minutes.

Referring to Figure 2, in addition to Figure 1, it will be seen that the timing of these cams and of the contacts operated by their switches |33 and 22, is as follows: At the beginning of the testing and listening interval, the operating spring of cam switch |33 rides up on an intermeiate elevation |34a of cam |34 (see Figure 2, a plane projection of the cam surfaces in which it is assumed that the cams are traveling from right to left) during this stage, which lasts 60 seconds, contacts |36 and |31 of cam switch |33 are closed but contacts |33 and |39 remain open until the end of the 60 second interval and the operating arm of the switch rides up on the highest elevation |341)y of the cam. When the last mentioned operation takes place contacts |38 and |39 close and remain closed for a period of 2O seconds, following which the operating member drops back to the intermediate level, thus opening contacts |38 and |39, for the next 40 seconds; contacts |35 and |31 remaining closed during the total two-minute period that the switch arm is displaced by elevations |34a and |3419. Cam |35 does not operate its switch |22 until the preliminary 60 second operating period of cam switch |33 is over, whereupon the operating member of cam switch |22 is shifted first by an intermediate elevation |35a of cam |35, for a period of 10 seconds, then to a top position |355 for a further period of 10 seconds (as will be apparent from Figure 2, these two successive 10 second periods correspond to the 20 second period during which contacts |38 and |39 of cam switch |22 are closed) and thereafter the operating member of cam switch |22 drops back to the intermediate stage |3511 for a further 10 second period, and then to its normal position.

In the normal position of cam switch |22, its contacts |20 and |2| are closed, but during the entire 30 second period during which the operating member of this switch is elevated by the intermediate and highest projections on the surface of cam |35, these contacts are open. On the other hand, contacts |2| and |45 of cam switch |22 are normally open, and are only closed when the operating member of the switch is engaged by the highest elevation |352) of the cam |35-i. e., so that contacts 2| and |40 are only closed during a 10 second interval.

Appreciating that these cam switch operations take place only once, in the described sequence during a two-minute interval every 15 minutes, it may be explained that during such interval the following operations take place: for the first 60 seconds, the receiving apparatus, relay amplifier, and oscillator, having their filament supply circuits energized, are permitted to heat up and reach operating condition, and thereafter for a period of 20 seconds, plate voltage is applied to the oscillator, so as to generate a test signal, and during the second half of that 20 second period, the alarm bell is conditioned to respond upon a failure of the test signal to energize the selective relay D. The plate voltage is subsequently removed from the local oscillator F, and for the final 30 seconds of the 2 minute period,

the receiving apparatus A is maintained in condition to listen for calls from a remote transmitter, the alarm bell being at the same time connected to indicate reception of such a call.

The operation of the various instrumentalities during this 2 minute period will now be described in detail. During the first 60 seconds, contacts |33 and |31 of cam switch |33 are closed, establishing the following circuit to energize relay lill, which is preferably a quick-acting type of relay: from the positive side of the 6-volt battery, through conductor 39, relay |4|, conductor |42, switch point |43, switch arm |44 of selector switch 2G (now in its central position), conductor |45, contacts |31 and |36 (now closed) and through conductors |45 and 30, back to the negative side of the 6-volt battery. Energization of relay |4| causes closure of its three sets of contacts. Closure of its contacts |41 and |43, causes the filaments of vacuum tubes 33 and 34 to be energized in parallel from the 6-volt battery; these contacts are in parallel with switch point 31 and switch arm 38 of selector swtch 2| (now open), and the energizing circuit for the vacuum tube filaments is otherwise the same as previously traced upon the closure of the switch point 31 and switch arm 38 when selector switch 2| was in its right-hand position. Contacts |49 and |55 of relay |4| are similarly in parallel with switch point 28 and switch arm 21 (now open) of selector switch 2|, and close the same circuit (previously described) to connect the power input of the radio receiver A with the 11G-volt line, as was closed when selector switch 2| was in its righthand position. Similarly, closure of contacts 5| and |53 of the relay |4| effect energization of the modulator magnet 14 and the microphone hummer |0 (in parallel), since contacts |5i and |52 are in parallel with switch arm 15 and switch point 11 (now open) of selector switch ZI-the circuit being the same as that previously traced for energization of the elements just identified, when the selector switch 2| was in its right-hand position.

Following the period of 60 seconds, during which the filaments or cathodes of the Vacuum tubes 33 and 34 and of the vacuum tubes in the receiving apparatus have reached their proper operating temperatures, the operating member of cam switch |33 rides up on the major projection |34b of the periphery of cam |34, for a period of 20 seconds. Closure of contacts |38 and |39 is thereby effected, establishing the following circuit: from the positive side of the B battery, through conductors 4I) and |53, contacts |33 and |39 (now closed), conductors 92 and 93, contacts 94 and 95 (now closed), and through conductor 93 to the plate circuit of the oscillator tube 33, and from the cathode of the tube to ground and thence via conductor 46 to the negative side of the B battery. Plate voltage is thus applied to the oscillator, and the latter accordingly sets up, and through the attenuator and coupling device 91a impresses upon the receiving aparatus A, the characteristic local signal. That is, since cam l1 is continuously driven by the motor l2, since the microphone hummer ||l has been energized, and since relay 14 has been energized to bring the modulating switch 8| into operative engagement with the cam |1, the radio frequency oscillations generated by oscillator F are modulated in accordance wth the characteristics to which selective relay D is adapted to respond-in the manner previously described with reference to the preliminary testing operation ffl and indicate reception oi such signal.

If the receiving apparatus, the relay amplier, the selective relay and their associated parts are functioning properly, they will respond to this local test signal, and relay D will be energized. Inasmuch as contacts |20 and |2| of the cam switch |22 are now open (see Fig. 2 and the previous description of the operation of cam |35), the alarm bell B will not now ring upon energization of relay D. During the second half, however, of this 20 second testing period, contacts |2| and |40 of the cam swtch |42 close, and if for any reason the selective relay D has not become energized by the test signal, the alarm bell will then be caused to ring, and will continue ringing until manually turned 01T by operation of the reset switch I Il. That is, if the selective relay D is energized, the resulting closure of its contacts |04 and |05 energizes relay |06, thereupon opening contacts H2 and |28 and closing contacts ||2 and ||3, but failing to operate the bell since contacts |20 and 2| are opened. On the other hand, if contacts |04 and |05 of the relay D are not closed, relay |06 will remain de-energized, and closure of cam switch contacts |2| and |40 will establish the following circuit: from the positive side of the 6-volt battery, through conductor 39, contacts |48 and |41 (now closed) of relay |4I, conductor |4, contacts l5 and ||6 (now closed) of reset switch conductor H8, contacts ||2 and |28 (now closed) of relay |06, conductor I3|, contacts |40 and |2| (now closed) of cam switch |22, conductors |23 and 12, alarm bell B, and through conductors 13 and 30, back to the negative side of the 6-volt battery. The alarm bell will thus be caused to ring, and by virtue of the stick circuit established by relay |24 (which has its winding in parallel with the bell B, as previously explained), the bell will continue to ring until the alarm reset switch 'l is manually oper- 1': ated. The attendant will thus be advised that something is wrong with the station.

If everything is in proper condition, however, the selective relay D responds, as previously eX- plained, to the local testing signal, and the bell does not ring. Thereafter, contacts |38 and |39 of cam switch |33 are opened, removing the B battery from the oscillator F, and contacts |2| and |40 of the cam switch |22 are likewise opened, to prevent operation of the bell upon deenergization of relays D and |06. In fact, during the next l0 seconds, control of the bell is entirely removed from relay |06, in either of its positions. At the end of that 10 second interval contacts and |2| are closed, so that the bell is now conditioned to ring if relay D, and consequently relay |05, are energized.

For the next seconds, the receiving apparatus and the relay amplifier are maintained in operative condition, and with the alarm bell conditioned for operation in response to energization of relays D and |0 in the manner just described, it will be seen that if signal is received from a remote transmitter during this 30 second interval, the alarm bell will be caused to ring In other words, this 30 second .interval constitutes an automatic listening period for such call-s as may be made to the station.

Thereafter cam switch |33 returns (as cam During the 13 minute 01T period, the receiving apparatus and the nlaments of the oscillator and relay amplifier tubes are de-energized, so that a very considerable saving is effected in energy consumption and in the life of the tubes and other elements of the apparatus.

Under some conditions, it may be desirable to have the receiving apparatus continuously in listening condition, as would be the case, for example, where the arrangement is employed for eiTecting an automatic alarm upon reception of an SOS call during ofi watch periods of a ship station. For continuous listening, the selector switch 20 is placed in its central or automatic position and selector switch 2| is placed in the central or continuous operation position. With the switches so arranged, the receiving apparatus and the relay amplifier are maintained continuously energized and operative; it being understood that switch arm 2l now engages switch point 20a (connected to point 28), to connect the power input with the receiving apparatus, and switch arm 3S engages switch point 3T@ (connected to point 3l), to energize the laments of the oscillator and relay amplier tubes 33 and 34-all in the same manner as when switch 2| was in its right-hand position. The cam switches |33 and |22, and other instrumentalities, intermittently operated by the cycling mechanism, continue their operation in the manner previously described, so that the microphone Y hummer I0 and the modulator relay 14 are preliminarily energized every l5 minutes, and thereafter plate voltage is applied to the oscillator F and a local modulated test signal is accordingly supplied by the latter to the receiving apparatus during the previously described 20-second period. This test, and the succeeding replacement of the various elements to normal listening oondition occur in the manner previously described during the interval that cam switch |22 is operated; if the alarm bell B commences to ring during the testing interval, warning is given that something is wrong with the receiving apparatus. At all other times contacts |20 and |2| of the cam switch |22 are closed, and since the receiving apparatus and the relay amplier are continuously energized, the station is connected for response to an incoming call. In other words, during 141/2 minutes, the station automatically listens for calls from a remote transmitter; during the remaining 30 seconds of each 15 minute period, testing operations are carried out in the manner described, to ascertain the condition of the apparatus.

In cases where it is desired to operate the receiving apparatus manually, i. e., Without the relay amplifier, or selective relay D, and so that the operator merely listens for calls with the loudspeaker |4, selector switch 20 may be set in its left-hand, or manual position, and selector switch 2| likewise set to its left-hand, or intermittent position. Inasmuch as the circuit of relay |4| is then permanently opened by the switch arm |44, and since no circuits are then closed by the selector switch 2|, the cycling mechanism will have no effect and neither the local oscillator, nor the relay amplier, nor the selective relay will be energized or operatively connected. At the same time, engagement of switch arrn 24 (of selector switch 20) with switch point |60, will connect the power input to the radio receiving apparatus A, energizing the same; and by virtue of the engagement of switch arm 52 with switch point |62, the loudspeaker |4 will be connected across the output of the receiving apparatus.

It should be noted that if a call comes in and causes operation of the alarm bell B when the receiver is Set for automatic listening-in operation (either continuously or intermittently), the operator may then receive the message in the usual manner, merely by depressing the alarm reset switch Ht for a moment, to turn orf the bell, and rotating' both selector switches 2i! and 2l to their left-hand positions. Manual operation of the receiving apparatus may then proceed, i. e., for reception of messages through the loudspeaker, and when the operator again goes olf watch he may restore the selector switches to their previous positions for continuing the automatic testing and listening operations.

It will now be appreciated that the supervision provided by the instriunentalities heretofore described is of a manifold nature. That is, the receiving apparatus is in effect tested for proper operating condition of all its parts; if, for example, the tuning of the receiver has been carelessly adjusted by the operator or if, because of vibration, ambient temperature effects, or other causes, the tuning of the receiving apparatus should change or creep, the apparatus will fail to respond to the test signal from the oscillator F, and the alarm bell will be rung. In similar fashion the alarm will be operated if any of the vacuum tubes of the receiver burns out or becomes deactivated, or if the power supply fails, or if a short or open circuit occurs anywhere, or as previously explained, if atmospheric or other disturbances are at Such a high level as to prevent proper automatic response to a call from theremote transmitter. The relay amplier E and the selective relay D are at the same time supervised in like manner, and it will be further noted that the remaining instrumentalities for monitoring the apparatus are, in an effective sense, self-supervised. 'Ihat if, if any of the parts of the oscillator F, or its crystal control, or its modulating devices (such as the microphone hummer IG, or the cam switch Si) should fail, the local signal will not be properly impressed upon the receiving apparatus, and consequently the selective relay D will not be energized during the testing interval, and the alarm bell will ring. Furthermore, as previously explained, the alarm bell is also connected to ring if the motor mechanism i2 fails to keep the cycling mechanism up to its prop-er speed of rotation.

It will be understood that as a further precaution, a separate battery, i. e., separate from the 6-volt battery shown, may be provided for operating the alarm bell B whenever such operation should take place. Similarly, a series relay can be included in the circuit of the 6-volt battery shown, arranged to substitute another battery or power source upon failure of the rst.

In Figure 3 a somewhat modied form of system is schematically shown. The radio receiving apparatus comprises the usual radio frequency amplifier 2%, detector and automatic volume control 2m, and audio amplifier 292, the loudspeaker or like communication translating device 23 being connected when desired, by closure of switch 2M, across the output of the amplier 282. In parallel with the loudspeaker there is also connected across the output of the amplifier 262 a further audio frequency amplifying stage 204 which is normally biased to cut-oif and is only active when a modulated signal is impressed upon the receiving apparatus. This last audio stage 296 may comprise, for example, a relay amplifier of the type designated E in Figure l. The receiving apparatus, including the automatic volume control, may be of any suitable type embodying the usual vacuum tubes and circuits, and having a power supply unit 295 for deriving the necessary receiver power from the line 295.

There is also provided a local source of modulated oscillations 207, which through an attenuating device 238 impresses modulated high frequency currents upon the receiving apparatus by means of the antenna coupling unit 2&39 associated with the receiver antenna lead 2HE. The oscillation source Zil' may be of any suitable type, for example, a crystal controlled vacuum tube oscillator modulated by a microphone hummer, such as the apparatus generally designated F in Figure l. Through the attenuator Zil, and by the adjustments of the oscillator and receiving apparatus, the oscillator is so connected to the receiving apparatus that the automatic volume control 2S! must vary to its position of maximum receiver response before the local signal, as set up by the oscillator 2537 and eventually amplified by the last audio stage 2815, will be of sufficient intensity to operate the relay 2li which is connected across the output of the last audio stage 2M. That is, the impressed local signal preferably has a predetermined low intensity which will require the automatic volume control to assume its position of maximum receiver response in order that the audio frequency modulating characteristics of the local signal, as amplified by the amplifier 20d, will effect sufficient energization of relay 2H to operate the latter.

In other words, when a carrier is not received from the distant transmitter M2, the automatic volume control will be in its position of maximum volume, and the signal locally generated by the oscillator 2557 will be normally received by the receiving apparatus, and will effect the predetermined sufcient energization of the relay 2H. In many cases, this relay need not be of selective type, and it is arranged to control an alarm bell 2I3, the latter being biased to operate, for example, unless the relay 2H is energized. rEhus when the receiving apparatus properly responds to the local signal, relay 2H is energized and the bell does not ring.

IIhe distant transmitter 2 I2, however, is adapted to transmit, to the receiver, an unmodulated calling carrier (or a carrier lacking any modulation to which the last audio stage 2M will respond) which is of such strength that the resulting signal intensity at the receiving apparatus compels the automatic volume control to vary from its condition of maximum receiver response to another value, and receiving operation on the local signal is correspondingly choked down to a point where relay 2 il is not energized. In other Words, reception of the anticipated unmodulated carrier, from the remote station, so affects the automatic volume control, e. g., by causing the latter to increase the grid bias on the radio frequency amplifying tubes, as to reduce the sensitivity of the receiving apparatus appreciably and at least to such extent that the audio frequency, i. e., modulation, characteristics, of the local signal fail to reach the last audio stage with suficient energy to effect the predetermined operating energization of relay 2 i i. At the same time, since the incoming signal, i. e. carrier, lacks the modulation to which the amplier 294 would respond, that signal itself, no matter how strong it is, will have no eiect towardenergizing relay 2H in consequence, relay 2H remains die-ener-V gized and the bell 2| 3 is caused to ring-thus indicating reception of call from the remote transmitter. lo

Y On the other hand, ii the local signal supplied by oscillator 201 fails to energize relay 2| Vfor any other reason-such as failure of any part of the receiving apparatus, or failure of the oscillator 201 to supply such local signal-the alarm bell 21:3 Will likewise ring, Warning the operator that his attention is needed. It will be appreciated that the local oscillator 201 is preferably tuned to set up oscillations at the same radio frequency asgthat to'which the receiving apparatus should be tuned for reception of the nii-modulated carrier from the remote transmitter 2l l.

A cycling mechanism may also belprovided, for example, of a motor-driven type like that shown in Figure lwhcreby the receiving` apparatus and the local oscillator 201 are turned on only at interrittent intervals for testing and listening purposes, the testing and listening operations being f conveniently simultaneous; such cycling mechanism would include provision, as by camoperated contacts, for interrupting the bell circuit during non-testing and non-listening periods. It Will also be appreciated that a manual Voperation switch may be provided, which would open the bell circuit, disconnect the local oscillator 201, and interrupt the operation of the cycling mechanism (if the latter is employed) so that upon reception o1" a call communication may be received via the loudspeaker 203.

In the arrangement shown inE Figure 1i, the output of the receiver 300 is connected in parallel to a non-selective relay 30| and a mechanically tuned selective relay 30,2, the latter being of any suitable type such as the selective relay D heretoforo identified in connection with Figure l. In this system, theV calling signal from the remote transmitter 303 consists ci a carrier modulated at a definite predetermined frequency, to which the selective relay 302V is tuned for response.

The local oscillator 300 impresses its local oscillations upon the antenna 305 of the receiver 300 by an inductance 305, and is conveniently designed to set up such oscillations at the same v radio frequency as that ci the carrier transmitted b the receiving apparatus 38? will energize the non-selective relay 3?.) which is so arranged that when yits winding is thus energized, the circuit of alarm, bell 301 is opened and the bell will not ring. On the other hand, the contacts of the selective relay 302 are arranged to close upon energizfation of that relay are conveniently connected in parallel with the alarm circuit-controlling contacts cf the relay 30i (normally open when relay 30! is energized). Thus when a :signal is received .from the remote transmitter 303, the selective relay 302 will be'energized, and closure of its contacts will close the alarm circuit and ring the l, l. gating reception of a calleren Ythough ihe Lie signal, or the locally gencratedY signal, Ymay at the same time energize relay Y30| as to open its corresponding alarm circuit contacts. On the other hand, if for any reason the non-selective relay 30| fails to become energized at a time when tie local oscillator 304 is supposed to be impressing a local testing signal upon the receiving apparatus 300, the alarm bell 301 will likewise ring, summoning the attendant for investigation.

It will be seen that in the arrangements shown in Figures 3 and 4, means are provided for testing the tuning ofthe receiving apparatus to a predetermined carrier, and for ringing an alarm in case of a failure of such tuning or of any other part of the receiving apparatus or its power supply, or in fact, in case of any failure of the local sourceY of testing signals 201 or 304' to supply the proper testing signal. Moreover, in the arrangement of Fig. 4, byY means Vof proper placement of the local oscillator or its output relative to the antenna 305, as at the far end of the latter,Y like supervision of the antenna itself is afforded; if, for insta-nce, the antenna 305 is carried away by a storm, there may be nothing to pick up, for the receiver, the locally radiated signal from the inductance 305, and consequently the bell will ring. l,

For some purposes, the relay 30| is preferably of the slow' release type, so that, for example, if a signal comes in at the proper radio frequency but modulated at some other low audio periodicity than that to which relay 302 will respond (e. g., a signal for calling another station), and if such signal should Vblock out the local signal from oscilla-tor 304, the opening of the contacts ofrrelay ,i will be sustained rather than periodically interrupted in accordance with the audio periodicity of such incoming signal,

In Fig. 5, the arrangement is generally the sai-re as that shown in Fig. 4, except Ythat thelsignaling means which is controlled in accordance with the supervision of the receiver 300 comprises a transmitter 308 conveniently having its own antenna and adapted, for example, to,.transmit a warning call Yto a remote station. That is, relays 30| and 302 are arranged to control separate circuits; the contacts of-non-selective relay 30| are included in the circuit which supplies .A or lamentcurrent to the tubes of transmitter 308 from battery .309, while the contacts of selective relay 302 control the circuit of. the foghorn 301a ergized, opening the energizingcircuit for transmitter n308, and keeping the transmitter 308 silent, but if something goes wrong, say, with the receiver 300, relay 30| will fail to receive the local test signal and will be deenergized, closing the circuit of transmitter A battery 30B and bringing the Ytransmitter 308 into operation. The transmitter 308 thus constitutes an alarmdevice, whereby a distinctive signal may be sent to a remote station upon failure of the receiving apparatus 300-an arrangement particularly useful where the receiver 300 is to be employed for remote control of apparatus such as a marine beacon, fog-horn or the like.

On the other hand, as explained in connection with Fig. 4, receptionnof the predetermined modulated signal Yfrom the remote transmitter 303 will operate relay 302 and in consequence the call bell 301 or such other device (light, horn or the like)Y as is to be operated by that signal; the local or the distant signal, or both, serving at the same-time to Ykeep non-selective relay 30| energized and the transmitter 308 silent.

The apparatus shown in Fig. 6 is essentially similar to that of Figs. 4 and 5, relay 30| being normally energized upon proper reception by receiver 303 of the local test signal from oscillator 304, and relay 362 being energizable to operate bell 301 only upon reception o1" the predetermined call signal from the remote transmitter 333. A spare receiving apparatus 3 l 3, conveniently having its separate antenna 3! l, is provided, and relay 38E is so arranged that upon its deenergization, as by failure of the receiver Sii@ to respond to the local test signal, contacts 312 and 3&3 of relay 3S! close, as shown, to connect the receiver power supply line 3M to energize receiver 3H), contacts 3i5 and 3H:` also close, as shown, to connect the selective relay 352 for control by the output of receiver SIU, and contacts SI5 and 3|1 open, removing the relay from its previous connection (with contacts 3l5 and Si? closed) in parallel with relay 3B! across the output of receiver 3230.

It will consequently be seen that upon failure of receiver 3M or its antenna 305, a spare receiver 3MB and antenna 3H are automatically brought into play for control of the relay 332 and thus for eiecting operation of the bell 36? or other device upon reception of the predetermined signal from the remote transmitter 333. It will now be appreciated that this arrangement, too, is of particular advantage in remote control systems, where there would be no attendant at the receiving station to make immediate repairs should anything go Wrong.

If desired, as in the case of Fig. 1, a cycling mechanism may be provided for automatic intermittent operation of any of the systems shown in Figs. 4, 5 and 6; and as will likewise now be understood, the systems of Figs. l and 3 can be readily adapted for automatic operation of an alarm transmitter or automatic substitution of a spare receiver upon failure of the receiver or its parts. t should further be noted that where the system of Figs. l, 3 or 4 are used as receiving stations of a remote control system, for example to operate a marine beacon, fogliorn or the like in lieu of the bells B, 2l3 or Si'l respectively, the system is biased, so to speak, on the side of safety. That is, if the receiving apparatus should fail, even at the crucial moment when it is desired to turn on the beacon or horn by a signal from the remote transmitter, the beacon, horn or other device will automatically be turned on (like the alarm bell shown) by reason of the receiver failure itself.

v Referring again to Figure l, more particularly, it may be noted that the local modulating means can be dispensed with where the receiving station is designed to respond to a call consisting of a simple unmodulated carrier,-i, e., the local oscillator F need then transmit only pure C. W. corresponding to the transmission from the remote station, and the arrangement would then also supervise such beat note generating devices as the receiver might include for proper reception of the pure C. W. It will also be noted that the alarm bell is arranged to lock in upon operation in response to a calling signal or in indication of a failure of any part of the apparatus during a testing period. By this arrangement, which may be employed with any of the other forms of the invention, the bell rings not only during actual calling or testing but continuously until the operator arrives to turn it oli". It will be further understood that the present invention may be conveniently applied to automatic radio telephone or like systems of the type disclosed and claimed in my hereinabove identified applications Serial Nos. 730,127 and 11,783, wherein in the lament and B battery leads to cause operation of an alarm (or substitution of another receiving apparatus) in case one or more vacuum tubes burn out or the batteries fail.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the cornbinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use within the scope of the appended claims.

I claim: v

l. In a radio signaling system, an alarm device, a local signal generator, wave receiving apparatus having an output circuit, means for causing said generator to impress a local signal upon the receiving apparatus and for conditioning said alarm device to operate, means for intermittently bringing said last mentioned means into play, means controlled by the output circuit of the receiving apparatus for preventing operation of said alarm device upon performance of normal receivcperations by the receiving apparatus upon the local signal, and means brought into play upon operation of the alarm device for preventing the intermittent means for interrupting operation of the alarm device.

2. A receiving station for a radio signaling system, comprising wave receiving apparatus adapted to effect predetermined receiving operations in response to predetermined waves having predetermined signaling characteristics from a remote transmitter, means including a local oscillator for setting up and impressing upon the receiving apparatus a local signal simulating said predetermined waves and including means for imparting said predetermined signaling characteristics to said waves, a control circuit, and means for effecting energization of said control circuit upon failure of the receiving apparatus to effect normal receiving operations upon the local signal set up by the iirst mentioned means.

3. In a receiving station for a radio signaling system, in combination, a test-responsive circuit adapted to effect a predetermined energization of an electrical device, wave receiving apparatus, supervising apparatus including means for applying to the receiving apparatus a local test signal of a character which the receiving apparatus is adapted to receive from a remote station, for opening said test-responsive circuit upon normal energized operation of the receiving apparatus in response to said local test signal, and means controlled by the receiving apparatus and in response to Waves of a predetermined nature, for closing said test-responsive circuit irrespective of the operation of said supervising apparatus.

4. In a receiving station for a radio signaling system, in combination, wave receiving apparatus adapted to establish a warning indication upon reception of waves modified with a predetermined signaling characteristic, and means for supervising the operation of said apparatus to effect a predetermined response upon failure thereof, said supervising means comprising means for applying to the receiving apparatus, a local testing signal comprising waves modified with said predetermined signaling characteristic and means for performing a predetermined circuit-controlling operation, and said receiving apparatus including means responsive to normal operation of said local signal applying means, for preventing operation of said circuit-controlling operation performing means, when the receiving apparatus is in normally energized operative condition, for its aforesaid response to waves modified with the predetermined signaling characteristic.

5. In a receiving station for a radio signaling system, in combination, wave receiving apparatus adapted to receive wave signals from a remote station and having an output circuit, and means for supervising the operation of said apparatus to effect a predetermined response upon failure thereof, said supervising means including means for applying to the receiving apparatus a local testing signal which comprises a carrier wave equivalent to that of a calling signal which said apparatus is adapted to receive, and said receiving apparatus comprising means responsive to normal operation of said local signal applying means, for effecting a predetermined energization of said output circuit when the receiving apparatus is in normally energized operative condition, and means associated with said receiving apparatus and responsive to reception thereby of a predetermined calling signal, for suppressing said predetermined energization of the output circuit.

6, A receiving station for a radio signaling system, comprising wave receiving apparatus, a relay controlled thereby and responsive to reception by the receiving apparatus of a predetermined signal from a distant transmitter, means including a local oscillator, for setting up and impressing upon the receiving apparatus a local signal simulating the aforesaid predetermined signal, control means adapted to bring said last mentioned means into play, an alarm device, and means responsive to operation of said control means for operating said alarm device upon failure ofthe aforesaid relay to respond to the local signal.

7. The combination of claim 6 in which the relay is a selective relay tuned for response only to a signal having a predetermined modulation, and in which the local oscillator has means associated therewith for imparting said predetermined modulation to the local signal.

8. The combination of claim 6 in which is included means having an actuating device therefor, for intermittently operating the control means to afford supervision of the receiving apparatus during the intervals of said intermittent operation, and governor means for operating the alarm device upon failure of the actuating device to actuate the intermittent operating means.

9. In a receiving station for a radio signaling system, in combination, a relay, Wave receiving apparatus having an input circuit for receiving signals from a remote transmitter, means for generating and impressing upon said input circuit a local test signal comprising radio frequency oscillations, said receiving apparatus including means controlled thereby for causing the relay to become energized upon reception of the local test signal by the receiving apparatus, and means under the control of the relay for effecting a predetermined emergency control upon failure of the relay to become energized when the local test signal is impressed on the aforesaid input circuit.

10. In a receiving station for a radio signaling system, in combination, an alarm device, Wave receiving apparatus having control means for effecting control of the alarm device therefrom, supervising means including a local radio frequency oscillator for impressing local oscillations on the receiving apparatus and means conditioning control means to operate the alarm device upon failure of the receiving apparatus to respond to the local oscillations impressed thereon, and means for conditioning the control means to operate the alarm device upon response of the receiving apparatus to a predetermined signal from a remote transmitter.

il. In a receiving station for a radio signaling system, in combination, wave receiving apparatus adapted to be set for response to calling signals from a remote transmitter, an alarm device, normally inoperative means for generating and impressing upon the receiving apparatus a local signal to which said apparatus is normally adapted to respond, normally inoperative means controlled by the receiving apparatus for causing operation of the alarm device upon failure of said receiving apparatus to perform normal receiving operations on the local signal, monitoring means for intermittently placing both said last-mentioned means in operative condition, whereby the receiving apparatus is intermittently supervised, alarm control means, and operating means therefor associated with said monitoring means and operable in response to failure of said monitoring means to eifect its aforesaid intermittent operation.

12. In a receiving station of a radio signaling system, in combination, normally deenergized wave receiving apparatus, means intermittently supplying energy to said apparatus to render it operative during the intervals of energy supply, a

relay, a source of local signals, means cooperating Withjsaidienergy-supplyingmeans ,for causing said source to impress a local signal upon the receiving apparatus during a portion of the intervals of energy supply, and means brought into play when said cooperating means is operative, for energizing said relay upon normal response of the receiving apparatus to the local signal.

13. The combination of claim 12, which includes a common driving motor for the intermittent energy supplying means and the means cooperating therewith, and also includes an alarm device and means for energizing the same upon failure of the motor to effect its aforesaid driving operation.

14. In a receiving station of a radio signaling system, in combination, wave receiving apparatus adapted to respond to radio wave signals, including waves having a predetermined modulation, means including a local oscillator for generating and impressing upon the receiving apparatus a local radio wave signal lacking said predetermined modulation, and means controlled by the receiving apparatus for indicating reception of waves from a remote transmitter having the predetermined modulation and for indicating departure of the receiving apparatus from normal operative condition irrespective of reception of waves from a remote transmitter, said last-mentioned means including selective relay means adapted to ciose an indicator circuit only upon response of the receiving apparatus to waves having the predetermined modulation, and relay means adapted to open an otherwise closed indicator circuit upon normal response of the receiving apparatus to the local radio wave signal at times when waves are not being received from a remote transmitter.

l5. In a receiving station of a radio signaling system, in combination, wave receiving apparatus including an automatic volume control device automatically variable to a position of maximum receiver response only upon reception of signals of no greater than a predetermined signal intensity, and an output circuit energizable under control of the receiving apparatus only by signals having an audio frequency modulation, said output circuit having means adapted to operate an alarm device unless said output circuit is energized at a predetermined energizing intensity at least as low as that resulting from reception by the receiving apparatus of signals having the aforesaid predetermined signal intensity, and means including a local oscillator and modulating means, for setting up and impressing upon the receiving apparatus a local signal that has a carrier frequency to which the receiving apparatus is adapted to respond, and that is modulated at a frequency capable of effecting energization of the aforesaid output circuit, and that is of no greater than the aforesaid predetermined signal intensity, whereby operation of an alarm device can be effected both upon failure of the receiving apparatus to respond normally to reception of the local signal and upon reception of an unmodulated carrier at least strong enough to cause the automatic volume control to prevent the local signal for energizing the output circuit at the predetermined energizing intensity.

I6. In a receiving station for a radio signaling system, in combination, wave receiving apparatus normally adapted for reception of signals from a remote transmitter, a second wave receiving apparatus, and supervising means for said firstmentioned receiving apparatus, said supervising means including a local oscillator adapted to introduce in the first-mentioned receiving apparatus oscillations adapted to effect a predetermined response of said apparatus upon normal operation of said apparatus, and means controlled by the first-mentioned receiving apparatus for controlling the second wave receiving apparatus to bringT the latter into operative condition for reception of signals from a remote transmitter, upon failure of the first-mentioned receiving apparatus to effect the said predetermined response tc the aforesaid oscillations.

ll. In a receiving station for a radio signali ig system, in combination, wave receiving apparatus, an alarm device comprising wave transmitting apparatus for transmitting a warning signal to a remote station, and means for supervising the operation of the receiving apparatus, said supervising means including a local oscillator adapted to impress local oscillations on the receiving apparatus, and means controlled by the receiving apparatus for effecting operation of said alarm device to transmit a. warning signal, upon failure of the receiving apparatus to effect a predetermined response to said local oscillations.

18. A receiving station of a radio signaling system, comprising Wave receiving apparatus adapted to be tuned for reception of signals of predetermined frequency from a remote transmitter, and means for supervising the response of said apparatus to signals of said frequency, including means for locally generating and impressing upon the apparatus a signal of said freduency, an alarm device having connections for control by the receiving apparatus in accordance with the response of the latter to the locally generated signal, and means for controlling the control of the alarm device by the receiving apparatus, said controlling means including a testing switch and being selectively settable to cause operation of the alarm device, independently of the testing switch, upon failure of the receiving apparatus to respond to the local generated signal, and to cause operation of the alarm device, in response to operation of the testing switch, upon normal response of the receiving apparatus to the locally generated signal.

19. In a radio wave receiving system, radio wave receiving apparatus, means for introducing local test signals in said apparatus, said apparatus including means for normally eecting a predetermining response of said apparatus to said signals, means limiting the intensity of reception of said local test signals whereby operation of said second-mentioned means is prevented when atmospheric disturbances received by said receiving apparatus have more than a predetermined intensity, and means controlled by the receiving apparatus for effecting a predetermined emergency control upon absence of said predetermined response to the local signals.

20. A method of supervising a radio receiving apparatus, comprising applying a signal of predetermined character and frequency to the input of said apparatus and thereby causing a predetermined response to said signal to be established by the output of said apparatus when the latter performs normal receiving operation on the signal, subjecting a control circuit to control by the output cf said receiving apparatus, causing said l control circuit to effect a predetermined emergency operation upon absence of the predetermined response tothe applied signal in the output of the receiving apparatus, and limiting the intensity of the applied signal to such level as will effect the aforesaid predetermined response only when atmospheric and like disturbances are below a predetermined level of intensity.

21. A method of supervising a radio receiving apparatus, comprising applying a signal of predetermined character and intensity to the input of said apparatus and thereby causing a characteristic response to said signal to be established by the output of said apparatus when the latter performs normal receiving operations on the signal, varying the intensity of said characteristic output response inversely in accordance With the intensity of other currents received by the input of said receiving apparatus, subjecting a control circuit to control by the output of said receiving apparatus, and causing said control circuit to effect a predetermined emergency control upon absence of oharaceristic response of at least a predetermined intensity in said ouput.

22. Means for revealing undesired detuning of a radio receiving system which comprises the combination with a radio receiving system tuned for response to Waves of a predetermined radio frequency from a remote station, of a local oscillator sharply tuned to produce waves of said predetermined frequency and having means for impressing said waves on the input of the receiving system, and means controllable by the receiving system for effecting a predetermined emergency control in response to failure of the receiving system to perform normal receiving operations on th'e waves produced and impressed by the local oscillator, whereby said emergency control will be produced unless both the local oscillator and the receiving system are tuned to the same radio frequency.

23. The combination of claim 22, wherein the local oscillator includes a piezo-electric crystal and connections for controlling the tuning of the oscillator thereby.

24. The combination of claim 22, which also includes a relay device under control of the receiving system for selectively effecting a predetermined control operation in response to reception of waves having a predetermined signaling modication, means associated with the local oscillator for impressing said predetermined signaling modification on the locally produced Waves, and means controllable by the relay device for bringing the predetermined emergency control means into operation in response to failure of the relay device to respond to the signaling modification of the locally produced waves.

25. In a receiving station for a radio signaling system, in combination, an alarm device, wave receiving apparatus having means for producing a predetermined control only upon reception of waves having a predetermined signaling characteristic, and supervising means for said apparatus, including means for locally generating testing waves and impressing same on the receiving apparatus, associated means for imparting the aforesaid predetermined signaling characteristic to the locally generated Waves, and means controllable by said predetermined control means for operating said alarm device upon failure of said receiving apparatus and its said control means to respond to the locality generated waves.

26. The combination of claim 25 wherein the supervising means is normally inoperative, and wherein are provided means for intermittently bringing the supervising means into operation to test the receiving apparatus at intermittent intervals, and means responsive to operation of the alarm device operating means, for thereafter maintaining the alarm device in operation, whereby the intermittent means is prevented from interrupting said operation.

27. In a receiving station for a radio wave signaling system, in combination, wave receiving apparatus adapted to respond to waves having a predetermined signaling modication and to waves lacking said predetermined modification, a signaling device, means for eiecting a predetermined emergency control, selecting means controllable by the receiving apparatus in accordance with its reception of both of said kinds of waves and simultaneously selectively responsive to operate the signaling device upon response of said apparatus to one of said kinds of Waves and to operate the emergency control means upon failure of said apparatus to respond to the other of said kinds of waves, and supervising means for locally generating and impressing on said apparatus the kind of waves for which failure of the receiving apparatus will cause the selecting means to operate the emergency control means, whereby the receiving apparatus may be supervised While it is listening for the other kind of waves.

28. In a receiving station for a radio wave signaling system, in combination, wave receiving apparatus having an automatic volume control circuit, a local generator for producing test signals, and impressing same on the receiving apparatus and having means for limiting the test signals, as applied, to an intensity which will cause variation of the volume control circuit to the condition of maximum receiver gain, means normally biased to elfect a predetermined emergency control, and means controllable by the receiving apparatus and responsive to normal receiving operation of the local test signal, for preventing operation of the last-mentioned means, whereby the emergency control will be effected upon reception of other waves having sufficient intensity to drive down the automatic volume control circuit.

29. In a receiving station for a radio signaling system, in combination, normally deenergized wave receiving apparatus, normally inoperative supervising means therefor comprising a local signal generator, means for producing a predetermined emergency control, and means controllable by the receiving apparatus for operating said last-mentioned means upon failure of said apparatus to respond to local signals from said generator, monitoring means for intermittently bringing said supervising means into operation, and means synchronized with said monitoring means for intermittently supplying energy to the receiving apparatus to render it operative during the intervals of energy supply, including the intervals of supervision under control of the monitoring means.

JOHN R. MACKAY.

OERTIMOATE OF CORRECTION. Patent No. 2,165,06LL. July in 1959.

JOHN R. MaoKAY. A

It is hereby certified' that error appears the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 65, for the reference numeral "75" read lYO; page 5,- first column, line 50, before "switch" insert reset; and second column, line 6h., for "test" read tests; page 6, second column, line 25, for swtch" read switch.; line 6h, for "aparatus" read apparatus; line 72, forV "wth" read with; page Y, first column, line ll, for "swtch" read switch; page 8, first column, line h2, for "That if" read That is; page lO, second column, line 148, claim l', for "for" read from; page l2, second column, line 18, claim 18, for "local" read locally; line 2?, claim 19, for "predetermining" read predetermined; page l5 first column, line )45, claim 25, for "locality" read locally; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of September, A. D. 1959 Henry Van Arsdale (Seal) Acting Commissioner of Patents 

